1. Field of the Invention
This invention relates to an improved process for the preparation of cycloalkyl aromatic hydroperoxides and is more particularly concerned with an improved process for the preparation of cyclohexylbenzene hydroperoxide and dicyclohexylbenzene dihydroperoxides.
2. Description of the Prior Art
It is known that cyclohexylbenzene can be converted to cyclohexylbenzene hydroperoxide by the autoxidation of cyclohexylbenzene in the absence of any catalyst; see U.S. Pat. No. 3,846,499. The latter process requires a first reaction temperature of 130.degree. to 150.degree. C. for 1 to 3 hours followed by a second reaction temperature of 105.degree. C. to 125.degree. C. for 2 to 4 hours. The selectivity is relatively low (of the order of 80 percent) because cyclohexylbenzene hydroperoxide can either decompose to 1-phenylcyclohexanol or rearrange to benzoylpentane derivatives.
It is also known that the autoxidation of cyclohexylbenzene can be carried out in the presence of a number of catalysts including t-butyl hydroperoxide; see Furukawa, Nenryo Kyokai-shi 40 (9), 711, 1961. The reaction was carried out at 110.degree. C. and the conversion was low (10.3%) with no details given of selectivity to the desired hydroperoxide.
Because of the nature of the autoxidation reaction, with formation of hydroperoxides which are potentially dangerous to handle in large scale operations, it is desirable to keep the reaction temperature as low as possible but at the same time to obtain satisfactory yields of cyclohexylbenzene hydroperoxide coupled with high selectivity of the latter in the overall reaction product.
We have now found that these objectives can be achieved by use of a free radical initiator in cooperation with certain hydroperoxides in the autoxidation of cyclohexylbenzene and dicyclohexylbenzenes as will be described in more detail hereinafter.